1. Technical Field of the Invention
The present invention relates generally to a gas sensor which may be installed in an exhaust system of an internal combustion engine for burning control thereof, and more particularly to an improved structure of such a gas sensor designed to reduce mechanical damage such as cracks to a sensor element which arises from a physical impact acting on the gas sensor.
2. Background Art
Some modern air-fuel ratio controls for automotive engines are equipped with a gas senor of the type, as taught in Japanese Patent First Publication No. 2002-174622, which is installed upstream of an exhaust pipe of the engine.
In recent years, regulations on exhaust emissions from automotive vehicles have been tightened, and with it there have been increased cases where the gas sensor is installed downstream of a catalytic converter of an exhaust system of automotive engines to monitor the condition of exhaust gas emitted from the catalytic converter.
However, when installed downstream of the exhaust pipe of the automotive engines, the gas sensor is usually exposed from the bottom of the vehicle body, thus resulting in an increased possibility of being subjected to physical impact such as hits from stones. When the stones hit an outer cover of the gas sensor, it may cause the cover to be deformed, which, in the worst case, results in cracks in the sensor element built in the gas sensor.
In order to withstand the impact, the cover of the gas sensor may be increased in thickness, but it results in an increased weight of the gas sensor and also difficulty in shaping the cover.